Bacterial brown stripe of rice, caused by Pseudomonas avenae Manns is a disease that affects rice seedlings. The symptoms of the disease on rice plants in the seedling stage were divided into 4 types: i.e. inhibition of germination, brown stripes on a leaf, curving of a leaf sheath and abnormal elongation of a mesocotyl. After the infected seedlings were transplanted to paddy fields, the symptoms were masked. Natural occurrence of the disease was not seen after the tillering stage, except for the case where rice plants were submerged in the water by flood. At the heading stage, the causal bacteria invaded the seeds during several days around the flowering date without any symptoms. A small quantity of the bacteria increased rapidly during the germination period and became the source of infection in nursery boxes in the following year. An effective method for controlling the disease is to maintain an adequate level of temperature and humidity each in growing rice seedlings and to use pathogen-free seeds with a germination test before planting. In case where the seeds are contaminated with the pathogen, it is important to control the disease by a bactericide of kasugamycin.